The physiological function and the mode of regulation of the transglutaminases are being studied. The roles of individual transglutaminases in cell membranes, in stimulation of specific cellular processes, and in connective tissue matrix stabilization are under investigation. A new transglutaminase apparently present in all cell membranes has been identified. It may function in chemotaxis and other cellular processes. The transglutaminase in uterus is derived from platelets. Together with fibronectin produced by uterine epithelia it may function in tissue stabilization.